General Motors Co. is offering a $25 coffee, movie or other gift card to entice owners of older-model small cars with defective ignition-switches to have their cars repaired by Dec. 1.

The auto maker sent letters to about 400,000 owners of Chevrolet Cobalt, Saturn Ions and other older vehicles offering a card that can be used at retailers including Starbucks, Red Robin Gourmet Burgers Inc. restaurants, Wal-Mart Stores Inc. and AMC...